Switch assembly and circuit for electrically heated bedcovers



April 12, 1966 c. F. JACOBSON SWITCH ASSEMBLY AND CIRCUIT FOR ELECTRICALLY HEATED BEDCOVERS Filed April 50, 1963 United States Patent Office 3,246,086 Patented Apr. 12, 1966 3,246,086 SWITCH ASSEMBLY AND CIRCUIT FOR ELECTRICALLY HEATED BEDCOVERS Chester F. Jacobson, Asheboro, N.C., assignor to General Electric Company, a corporation of New York Filed Apr. 30, 1963, Ser. No. 276,929 8 Claims. (Cl. G5)

This invention relates to integrated multiple switch constructions, and in particular to an electrical control switch assembly to energize an electrically heated device, such as a bedcover, and a safety control circuit therefor.

For electrically heated bedcovers and the like, an overtemperature protective circuit is a highly desirable safety feature for its operation to deenergize the electrical heater upon any over-temperature condition. Typically, such a protective circuit includes an electromagnetically operated switch to maintain the circuit closed for normal operating conditions, but which releases and opens the electric heater circuit upon any abnormally high operating temperature. The manual actuator used to energize initially the electromagnetic means, for complete protection, must be arranged so that the heating device can be operated only when the protective circuit is fully operative. Even intentional jamming of the manual actuator must not be effective to defeat the safety control.

Accordingly, it is an object of my invention to provide an improved, manually operated, switch assembly and circuit for an electrically heated bedcover and safety control therefor.

It is a further object of this invention to provide a switch assembly wherein the operation of one or more push buttons to close their respective switches additionally insures proper sequential operation of a safety control switch.

It is yet another object of this invention to provide such an assembly wherein the push buttons are designed to preclude accidental jamming of the control switches.

It is a still further object of this invention to provide a durable push button switch assembly capable of withstanding repeated push button operation and at a minimum manufacturing cost.

In carrying out the objects of this invention in one form thereof an electrically heated bedcover switch assembly is provided utilizing a pair of manual actuators for respective, normally open, on and off switches in an assembly housing. Additionally a normally closed safety switch is provided having a movable contact arm positioned between the movable elements of the on and off switches to open the heater or load circuit upon initial movement of either or both of the manual actuators. Thus, the load circuit remains open upon any attempt to hold or jam either of the manual controls in an actuated or closed position. Means are provided on the terminal board to which the fixed contacts of the on and off switches are secured so that the operating force of the push button or manual actuator is transmitted through the terminal board to the assembly housing. Furthermore, each push button, the terminal board and portions of the assembly housing cooperate to insure substantially axial reciprocal motion of the push buttons in the housing.

Further objects and advantages of my invention may best be understood by reference to the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a perspective view of the control switch assembly;

FIG. 2 is a partial sectional view of the control switch assembly taken on line 22 of FIG. 1;

FIG. 3 is a partial sectional view of the control switch assembly taken on line 3-3 of FIG. 1;

FIG. 4 is a perspective view of certain elements of the control switch assembly showing all switch elements in their normal position; and

FIG. 5 is similar to FIG. 4 except that the switch elements are shown in their position upon depression of one push button and a typical electric bedcover heating circuit in which the switches may be used is shown.

Referring now to the drawings, FIG. 1 shows a control housing 10 of plastic or other suitable rigid, insulated, material. The device shown by FIG. 1 is, typically, the bedside control unit for an electric bedcover having a rotatable knob 9 for temperature selection. Housing 10 also includes a pair of apertures 11 and 12 which respectively accommodate actuators or push buttons 13 and 14 of on and off switches to be described.

FIGS. 25 reveal the structure and operation of the elements of the control switch assembly within housing 10. Push button 13 is positioned so that the manual depression thereof through aperture 11 closes an on switch comprising a resilient conductive switch arm 15 and a fixed contact 16. Likewise, the depression of push button 14 closes an off switch comprising a resilient conductive switch arm 17 and a fixed contact 18. A safety switch, including a generally U-shaped conductive contact member 19 and a fixed contact 20 is operable to an open position, upon depression of either push button 13 or 14. These movable and fixed switch elements are secured to a terminal board 21. Terminal board 21, in turn, is secured to housing 10 by a single suitable fastener 22.

As is clear from FIGS. 4 and 5, safety switch member 19 is generally U-shaped and provides one arm 19a secured at 23 to the terminal board and a second arm 19b which may carry a current contact at its free end or contact portion for normal engagement with fixed contact 20. Arms 19a and 1% are joined by a base 19c. A fulcrum 24, which may be integrally formed with terminal board 21, is intermediately positioned beneath arm 1% over which arm 19b pivots. A reinforcing rib 25 is provided along base 19c and arm 19b of switch member 19. It is to be understood that fulcrum 24 is utilized in cooperation with reinforcing rib 25 to increase reliability of switch operation. Fulcrum 24 may be omitted when the reinforcing rib is used, as arm 19b will still pivot about a fulcrum in space upon depression of base 190.

The corners of base of the safety switch member lie adjacent the free ends of switch arms 15 and 17 and are engaged by radial flanges 26 and 27 of their respective push buttons. It is therefore clear that flanges 26 and 27 provide means for respectively linking or interconnecting actuators 13 and 14 to the base 190 of the safety switch so that inward movement of either of the actuators pivots the arm 19b to separate the contacts of the safety switch. The corners of base 190 may normally assist switch arms 15 and 17 in biasing the push buttons to their outer inoperative positions.

To insure the axial motion of each push button within its respective aperture, and to transmit the forces of depression of the push buttons from the switch elements to the housing, each push button, the terminal board 21 and the assembly housing 10 provide vinterfitting elements. As the structure relating to each push button is exactly the same, only the features of one push button will be described.

Push button 13 is cylindrical and provides an eccentrically located axial projection 28 as well as radial flange 26. Preferably, projection 28 and flange 26 are integrally molded with the cylindrical portion of push button 13. Housing It) provides a semi-cylindrical guide 29 which extends coaxially with push button 13 to partially encompass the push button. The internal end of guide 29 incorporates a radial flange or support surface 30 which defines a groove 31.

As best seen in FIGS. 4 and 5, terminal board 21 provides an ear 32, having a recess 33, for each push button. Terminal board 21 is secured to housing so that ear 32 lies within guide 29, in juxtaposition with radial flange 30 so that recess 33 is axially aligned with groove 31 to form an aperture therewith.

FIGS. 5 shows schematically a typical electrically heated bedcover circuit for which this switch assembly is particularly adapted. Power is supplied for operation through terminals 34 and 35 arranged to be connected in the usual manner to an electrical power source. The control circuit includes a relay having coil 36 for operating a switch 37 when the relay coil is energized. For an electric blanket application, a suitable resistance heating element 38 is distributed in a well-known manner over the heating area. The load circuit for supplying power to electric heater 38 may be traced from line terminal 34, through the heater, a terminal of the safety switch, U-shaped conducting arm 19, through safety switch contact 20, conductor 41, relay switch 37, and conductor 42 to the other terminal 35 of the power source. It may be noted from this circuit that both the safety switch, comprising U-shaped member 19 and contact 20, and the relay switch 37 must be closed for power to be supplied to heater 38.

Overtemperature protection for this electrically heated device is provided by a temperature sensor arrangement including distributed conductors 43 and 44, which extend in proximity to one another, separated however, by a layer of material 45 which is an insulator at normal operating temperatures and a conductor of electric current of control magnitude upon occurrence of any abnormally high temperature. During normal operation, relay coil 36 is energized through a control circuit commencing with power terminal 34, sensor conductor 43, a connecting lead 46, relay coil 36, conductor 47 to a resistor 48. From the other terminal of resistor 48, a connection is made through lead 49 to the other conductor 44 of the temperature sensor assembly, then through conductor 50 to a voltage dropping resistor 51 and through relay contacts 37 to the other side of the power source. From this circuit, it may be noted that the relay may remain closed even though on switch 16 is in its normally open condition. Upon occurrence of any abnormally high temperature, conduction takes place through the temperature sensing layer 45, which results in a drop in the voltage applied to relay coil 36, and the relay coil, therefore, releases its armature, and switch 37 opens the circuit to both heater 38 and the blanket control system.

On switch 1516 provides a means for initially energizing relay coil 36 through a circuit commencing with power line 34, conductor 43 of the temperature sensor assembly, connecting line 46, relay coil 36, and conductor 47, to on switch contact 16. When on button 13 has been depressed, the circuit is completed through spring arm 15 of the on switch, a conductor 52, a current limiting resiStOr 53 to the other terminal of the power source 35. T e size of the resistor 53 is, of course, selected to apply adequate voltage to the relay coil, so that it will close the relay switch 37. Thereafter, the relay remains closed under normal operating conditions through the circuit previously described. It should be noted particularly, however, that the heater 38 is ineffective as long as the on switch is even partially depressed, since the initial movement of the on push button opens the safety switch at contact 20.

The user occasionally desires to deenergize the heater and control circuit manually by means of push button 14. While the off button could operate in several different ways, as shown in FIG. 5 the closing of the off switch provides a shunt circuit around relay coil 36, conductor 47 and resistor 48. The shunt circuit is through conductor 54, off switch contacts 18 and 17 and conductor 55. Hence, when the off switch is closed, there can be essentially no voltage on the relay coil, upon which the relay switch opens.

In accordance with this invention, it should be noted particularly, however, that the actuation of oif push button 14 opens the heater circuit through the safety switch at contact 20 prior to the time that relay switch 37 opens. This is a desirable feature, since the relay for this purpose must be very carefully calibrated. This calibration will remain accurate for a longer period of time if its switch is not required to frequently interrupt heater line current. With this arrangement, as above described, the safety switch interrupts line current on any manual actuation of the off push button; whereby relay switch 37 is required to interrupt line current only upon an abnormal overtemperature condition. Of course the re lease of on pushbutton 13 also closes the heater circuit through the safety switch.

The sequence of switch operation, whereby the safety switch member is pivoted to an open position prior to closing of the switch arms 15 or 17 against their respective fixed contacts, is obtained by the interrelation of the switch elements, particularly the position of fixed contacts 16 and 18 on one side of fulcrum 24 and the mounting of contact 20 on the other side of the fulcrum. By this arrangement depression of either push button immediately opens the safety switch, a complete depression of the push buttons being required for closing of the respective on" and oif switch.

During the axial motion of the push buttons through their respective housing apertures, axial projections 28 are are accommodated in the aperture provided by the relationship of groove 31 and recess 33. This controls the path of the push buttons thereby insuring substantially axial motion thereof to prevent accidental jamming of the push buttons, which might otherwise result from application of an off-center force to a push button.

It can be seen that the depression of push button 13 to close switch member 15 against its fixed contact 16 applies a pressure to the terminal board 21. The positioning of ear 32 of the terminal board against radial flange 30 transmits this push button pressure to the housing 10. Also, the inward movement of the push buttons is thus limited by the engagement of the switch members with their respective fixed contacts. The outward movement of the push buttons is limited by the engagement of respective radial flanges 26 and 27 with the inner surface of the housing which defines apertures 11 and 12 respectively. The upper surfaces of radial flanges 26 and 27 also serve to limite the rotation of the push buttons by engagement with the lower surfaces of housing guide 29.

I have thus provided a manually operated control switch assembly, which prevents the users accidental or intentional defeat of a safety circuit by jamming an actuator in a closed position. Furthermore the switch assembly elements are designed to cooperate to insure substantially axial motion of the push buttons and to transfer the forces of operation of the push buttons from the terminal board to the assembly housing.

While I have shown and described a specific embodiof my invention, I do not desire my invention to be limited to a particular construction shown and described. Instead, I intend, by the appended claims, to cover all modifications within the spirit and scope of my invention.

I claim:

1. In an electric bedcover control a switch assembly comprising:

(a) a housing defining a pair of apertures;

(b) first and second push buttons received in the apertures of the housing for movement of said push buttons to outer and inner positions;

(c) an on switch including an electrically conducting member cooperating with said first push button for movement therewith and an electrical contact, said electrically conducting member and said contact being engaged with each other when said first push button is moved to an inner position, and disengaged when said first push button is moved to an outer position;

(d) an off switch including an electrically conducting member cooperating with said second push button for movement therewith and an electrical contact, said electrically conducting member and said contact being engaged with each other when said second push button is moved to an inner position, and disengaged when said second push button is moved to an outer position;

(e) a safety switch including a pair of contacts which are engaged with each other when said push buttons are in an outer position, and further including a movable arm carrying one of said safety switch contacts; and

(f) means linking each of said push buttons to said movable arm of said safety switch for separating said safety switch contacts prior to engagement of the electricaly conducting members and their respective contacts when either one of said push buttons is moved from an outer to an inner position.

2. The switch assembly as set forth in claim 1 wherein said electrically con-ducting members of said on and off switches each comprises a flexible arm.

3. The switch assembly as set forth in claim 1 wherein said safety switch comprises a resilient U-shaped contact member including a first arm connected to the housing, a second arm pivotally mounted about a fulcrum, and a base portion connecting said arms, said second arm providing a contact carrying portion on one side of the fulcrum and said base portion being on the other side of the fulcrum for said linking means to engage said base portion and pivot said arm about said fulcrum upon inward movement of either of said push buttons.

4. The switch assembly as set forth in claim 3 wherein said U-shaped contact member includes a re-inforcing rib extending along said base and along said second arm.

5. The switch assembly as set forth in claim 1 wherein said switches are mounted on a terminal board secured to the housing, and said fulcnlm comprises a projection spacing the center portion of said movable arm of said safety switch from the surface of said board.

6. The switch assembly as set forth in claim 1 wherein said housing provides means for guiding a movement of each of said push buttons and for receiving the force of said movement upon actuation of switches.

7. In an electric bedeover control, a switch assembly comprising:

(a) a housing defining an aperture;

(b) a push button received in said aperture for movement of said push button to outer and inner positions;

(c) a first switch including an electrical conducting member and a contact separated from each other when said push button is in an outer position, said electrically conducting member cooperating with saidpush button to engage the contact when said push button has been moved to an inner position;

(d) a second switch including a pair of contacts engaged with each other when said push button is in an outer position, said second switch comprising a resilient U-shaped contact member including a first arm connected to the housing, a second arm pivotally mounted about a fulcrum, and a base portion connecting said arms, said second arm carrying one of said contacts on one side of said fulcrum, and said base portion being located on the other side of said fulcrum;

(e) linking means for linking said push button to said base portion of the U-shaped contact member for pivoting said second arm to disengage said second switch contacts when said push button is moved from an outer to an inner position.

8. The switch assembly as set forth in claim 7 wherein said switches are mounted on a terminal board secured to the housing.

References Cited by the Examiner UNITED STATES PATENTS 2,806,907 9/1957 Mazzola 200-5 2,879,345 3/1959 Mossman 200-5 2,935,590 5/1960 Jacobs et al 219-204 2,987,602 6/1961 Hodges 21920.4 3,137,773 6/ 1964 Black 200-5 KATHLEEN H. CLAFFY, Primary Examiner.

RICHARD M. WOOD, Examiner.

L. H. BENDER, M. GINSBURG, Assistant Examiners, 

1. IN AN ELECTRIC BEDCOVER CONTROL A SWITCH ASSEMBLY COMPRISING: (A) A HOUSING DEFINING A PAIR OF APERTURES; (B) FIRST AND SECOND PUSH BUTTONS RECEIVED IN THE APERTURES OF THE HOUSING FOR MOVEMENT OF SAID PUSH BUTTONS TO OUTER AND INNER POSITIONS; (C) AN "ON" SWITCH INCLUDING AN ELECTRICALLY CONDUCTING MEMBER COOPERATING WITH SAID FIRST PUSH BUTTON FOR MOVEMENT THEREWITH AND AN ELECTRICAL CONTACT, SAID ELECTRICALLY CONDUCTING MEMBER AND SAID CONTACT BEING ENGAGED WITH EACH OTHER WHEN SAID FIRST PUSH BUTTON IS MOVED TO AN INNER POSITION, AND DISENGAGED WHEN SAID FIRST PUSH BUTTON IS MOVED TO AN OUTER POSITION; (D) AN "OFF" SWITCH INCLUDING AN ELECTRICALLY CONDUCTING MEMBER COOPERATING WITH SAID SECOND PUSH BUTTON FOR MOVEMENT THEREWITH AND AN ELECTRICAL CONTACT, SAID ELECTRICALLY CONDUCTING MEMBER AND SAID CONTACT BEING ENGAGED WITH EACH OTHER WHEN SAID SECOND PUSH BUTTON IS MOVED TO AN INNER POSITION, AND DISENGAGED WHEN SAID SECOND PUSH BUTTON IS MOVED TO AN OUTER POSITION; (E) A SAFETY SWITCH INCLUDING A PAIR OF CONTACTS WHICH ARE ENGAGED WITH EACH OTHER WHEN SAID PUSH BUTTONS ARE IN AN OUTER POSITION, AND FURTHER INCLUDING A MOVABLE ARM CARRYING ONE OF SAID SAFETY SWITCH CONTACTS; AND (F) MEANS LINKING EACH OF SAID PUSH BUTTONS TO SAID MOVABLE ARM OF SAID SAFETY SWITCH FOR SEPARATING SAID SAFETY SWITCH CONTACT PRIOR TO ENGAGEMENT OF THE ELECTRICALLY CONDUCTING MEMBERS AND THEIR RESPECTIVE CONTACTS WHEN EITHER ONE OF SAID PUSH BUTTONS IS MOVED FROM AN OUTER TO AN INNER POSITIONS. 